SSAH File Shredder is a fully DoD-522022m specification compliant file shredder. It is a specification for how a file is to be securely erased. It entails writing over all of the data area of the file with 1's (FFh) then writing over it all again with 0's (00h). According to spec, this procedure is repeated 3 times. Then finally, the is overwritten with the value of F6h (11110110).

When you delete a file, all that happens is that the first character in the file allocation (FAT) table is changed to reflect that it has been deleted. At this point, it is still possible to UNdelete the file, with any number of tools, allowing a full recovery of the file. Over time the file data would become overwritten after it was deleted, and eventually only some of the data would be retrievable, and finally, none.

Because hard drives are magnetic storage media, the data that is recorded often leaves a magnetic trace, even after it has been "deleted" AND overwritten. If you deleted a file, and then saved data over that portion of the hard drive, in most cases all or most of the data would still be recoverable with special hardware. This hardware looks for the magnetic traces of the old data and reconstructs the file as it was.

The point of all the 1's and 0's then, is to set and clear every magnetic bit used to store the file several times. The expectation is that this will be enough to prevent reading the data, which has been overwritten and cleared multiple times. Imagine a chalkboard, if you were to write on it, and then erase it, you would usually still be able to read what had been written. If you then wrote on it again, you would still be able to read most of what had been there. But now, cover the entire board with chalk, and then erase the entire board, three times... and you have little hope of reading what had originally been written.

The license of this software is Freeware, you can free download and free use this file shredder software.